The present invention relates to a pack designed to be attached to the platform of a bicycle rear carrier rack.
Recreational bicyclists often carry food and cold drinks and items such as cameras and binoculars with them when bicycling, and bicycle packs of various kinds for such articles are widely available. A popular bicycle pack is one that rests on top of and is secured to the platform of a rear carrier rack, which can be termed a "rackpack." The state-of-the-art rackpacks, which are produced by several manufacturers, are bags about the same width and length as the rack platform and of suitable height, say 6 or 9 inches, with hook and loop cloth straps, one at each corner of the bottom, to fasten the rackpack to bars of the platform. Rackpacks are made of a suitable fabric and have tops that open along one, two, or three edges via a zipper closure for access to the interior.
It is well known among experienced cyclists that all packs and the gear in them should be secured to the bicycle as immovably as possible. In the case of rackpacks and panniers, any swinging or swaying of the packs or the gear from side to side produces "tail-wagging" of the bicycle. The increased balance and steering efforts to offset the tail-wagging use the cyclist's energy unnecessarily.
"Soft" rackpacks, i.e. ones that do not have a fixed shape, are especially prone to cause tail-wagging if the gear they hold is not carefully packed, and indeed, sometimes when they are carefully packed. The flexibility of the fabric is poorly suited to restrain movement of the contents. The load is relatively high on the bicycle so that side sway of the bicycle subjects the load to considerable movement. Furthermore settling of the content of a soft rackpack often results in part or all of the pack and its content hanging to one side or the other, unevenly loading the bicycle.
The art has foreseen the usefulness of providing thermal insulation in rackpacks and has stitched sheets of flexible polymeric foam into the bottom, top and walls in the manner of soft cold drink packs available for general use. Conveniently, the foam sheets also increase the stiffness of the walls somewhat, which then provide some control of the load for reduced tail-wagging. Nevertheless, considerable flexibility remains, especially in the upper part of the pack where it is not firmly affixed to the rack. While these thermal rackpacks insulate better than a standard rackpack, they are not water tight at the seams, so if the user adds ice, to keep beverages cold, for example, the water from the melting ice can drip down on the bicycle parts below. Resulting wetness of the bag itself makes it likely to pick up dirt from the ground or another resting place. Such wetness also detracts from the desirability of converting the pack to a portable carrier. If the rackpack has external pockets, the water can soak into them to wet whatever gear they contain.